ANALYTICAL MECHANIC'S which distinguishes the pivot from the journal bearing is this: in the former the lever arm of the Motional force varies from point to point, while in the latter it is constant and equals the radius of the shaft. Let dN be the normal reaction upon dA, an element of area at the base of the flat-end pivot of Fig. 39; then if dF denotes y the corresponding frictional |£ force, we h&ve where p is the normal pressure. Evidently p is constant; therefore we can write ra* dA PICK 31). The expression for the resisting torque due to the friction is obtained as follows : XF r-dF . XA r*np n2?r r/rp- rdO*dr - = f where P is the total load on the pivot.